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Posted: June 15, 2009

Carbon nanotubes may lower cost of fuel cells

(Nanowerk News) The high cost of manufacturing fuel cells makes their large-scale production for power generation next to impossible, but researchers at Arizona State University are working to change that so cars, electricity and much more can run on the “green” technology.

Engineering technology professor Arunachalanadar Madakannan (Kannan) has been studying the proton exchange membrane fuel cells (PEMFC) for more than eight years. The fuel cells Kannan and his graduate students are focusing on employ carbon nanotube-based catalysts and electrodes.

Fuels cells, which cleanly and quietly generate electric power by passing fuels like hydrogen over one electrode while passing air over a second electrode, have been around for more than 100 years. But their development has long been dogged by costs of the technology as well as safety concerns.

Kannan said PEMFC fuel cells have layers of electrode and electrolyte components. In a PEMFC, the cell is made up of an hydrogen-based anode (positive) terminal and oxygen-based cathode (negative) terminal, with carbon-particle supported platinum acting as a catalyst (electrode) to produce power. While fuel cells produce electrical energy, the only waste generated is water, so it’s considered a very clean energy conversion system.

Scientists have been honing fuel cell technology since its inception, but, even after more than a century, the cost of producing fuel cells remains high because of the platinum-based catalysts.

“Platinum is the most effective electrocatalyst and a good conductor of electricity in fuel cells, but the cost is so prohibitive that we have not yet been able to use fuel cells widely,” says Kannan, an associate professor in the College of Technology and Innovation at ASU’s Polytechnic campus.

Kannan is working to create lower cost PEMFCs by directly growing carbon nanotubes on carbon paper substrates, otherwise known as the gas diffusion layer, rather than spherical carbon particles and then deposit platinum nanoparticles onto the surface of the nanotubes. This innovative approach allows for the use of less platinum, without impacting energy efficiency.

“This modified process saves about 10 to 15 percent of the cost compared to what exists today, without sacrificing any power output,” says Kannan.

During his research, Kannan was evaluating the performance of several different materials, measuring power output and efficiency along the way.

“The carbon nanotube-based electrode is more efficient because it has a greater surface area,” says Kannan, “which allows for less platinum to be needed. In addition, the electrodes also perform extremely well under lower relative humidity, which will ultimately reduce the fuel cell system complexity.”

Kannan co-authored three papers on the topic, which were all recently published in the Journal of Power Sources as well as the International Journal of Hydrogen Energy.

In addition, ASU and Helsinki University of Technology along with VTT in Finland have entered into a project regarding an advanced material solution for PEMFCs. Currently ASU graduate student Chad Mason is in Finland testing and improving the performance of the gas diffusion layer materials, while lowering costs and increasing manufacturability.

“The next step is to make the development of the gas diffusion layer continuous, rather than a batch process, so that it can be commercially viable,” says Kannan. “Chad’s work overseas will allow us to move in this direction. We believe that PEM fuel cells will become commercially viable in a decade or so and help us move toward a hydrogen economy.”